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Muriatic Acid: 1. Mill Scale: 0

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Muriatic Acid: 1. Mill Scale: 0

Postby RayCJ » Thu Oct 12, 2017 6:25 pm

Finally, after a couple decades, I built a dedicated bench for welding. In the past, I used the floor or rigged a makeshift table from saw-horses. Now I know how caveman felt after inventing fire, round wheels and cooked meat. Anyhow, I covered the top with a piece of 11ga HR and found myself struggling with bad grounds because of the millscale. A quick internet search lead me to using muriatic acid (aka HCL) which I happened to have laying around.

WOW! Works great! 15 minutes later it went from black/grey tough millscale to looking like a sheet of stainless steel.

NOTES OF CAUTION: The Muriatic acid used for swimming pool Ph control and concrete etching will cause severe chemical skin burns. Mixed with the wrong chemicals, it can create fumes that could be fatal. If you use this stuff (it's available at lowes and home depot in the paint section) do it out in the open where you have a garden hose to flush things down. Expect that it will kill any vegetation and leave bleached marks on all surfaces it contacts.

Anyhow, the tabletop is 2.5 x 5 feet. I unrolled paper towel and lined the top and slowly poured the HCL onto the sheets. The sheets absorb it and keep it in-place w/o running off. At best, it took a pint or a little more.

Here's a few quick snaps of the table and few extras of the new Vulcan welder which I used to build the table and the new cart. Also, you can see the "before" shot of the millscale -but I suspect most folks already know what it looks like.


IMG_20171012_180917.jpg
New Vulcan and Cart
IMG_20171012_180917.jpg (82.38 KiB) Viewed 540 times

IMG_20171012_180518.jpg
Table w/Etched Surface
IMG_20171012_180518.jpg (46.45 KiB) Viewed 540 times

IMG_20171012_180549.jpg
Nice and Pretty after 2 mins with the flap disk.
IMG_20171012_180549.jpg (29.85 KiB) Viewed 540 times

IMG_20171012_180936.jpg
Bad, Ugly Millscale.
IMG_20171012_180936.jpg (50.23 KiB) Viewed 540 times


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Re: Muriatic Acid: 1. Mill Scale: 0

Postby cj737 » Thu Oct 12, 2017 10:55 pm

Interesting. I’ve always operated under the belief that you add Acid to Water, never the reverse. By rinsing the Acid, if it’s still “active” you risk potential “explosion” of the Acid. I would have thought you would wet the table, then pour acid onto it (add paper towels if desired, then let work. It would then be safe to flush/rinse with water.

At least that’s the method I’ve used with Acid when etching or cleaning a surface.

Your table turned out nice though :)
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Re: Muriatic Acid: 1. Mill Scale: 0

Postby motox » Fri Oct 13, 2017 6:18 am

ditto, acid to water not the reverse....
how do you like that Precision-Mattews mill?
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Re: Muriatic Acid: 1. Mill Scale: 0

Postby LtBadd » Fri Oct 13, 2017 6:50 pm

motox wrote:how do you like that Precision-Mattews mill?

I was wondering the same, have been looking at this on the web
Richard

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Re: Muriatic Acid: 1. Mill Scale: 0

Postby RayCJ » Fri Oct 13, 2017 7:08 pm

The PM mill and other equipment in general is fine. The one seen in the background is about 10 years old and has seen countless hours of use while I ran my fabrication business before going into semi-retirement. Matt (from Precision Matthews) is a great guy. I'm a little biased though because, for a couple years, I was affiliated with his business. That said, I went from an old Bridgeport to the PM 45 and life improved a good bit thereafter. I have a PM lathe as well that has seen 5x as much mileage as the mill. I can still dial-in and keep 5 tens.

As for the acid... Not sure where people got the impression I was attempting to dilute it. Simply not the case. I was using it full strength. FWIW, the stuff available at Lowes (which is what I happen to have) is a 30% solution. As I recall during my college days, only higher mole fraction solutions tend to flash-over.

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Re: Muriatic Acid: 1. Mill Scale: 0

Postby motox » Sat Oct 14, 2017 5:20 am

Raycj
i bought a PM 25 unit and though its small its very accurate and works great for the small parts
i need to fab. since retiring and relocating my shop space is considerably smaller so my tools
need to fit my space.
craig
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Re: Muriatic Acid: 1. Mill Scale: 0

Postby RayCJ » Sat Oct 14, 2017 7:28 am

motox wrote:Raycj
i bought a PM 25 unit and though its small its very accurate and works great for the small parts
i need to fab. since retiring and relocating my shop space is considerably smaller so my tools
need to fit my space.
craig


Those PM25's sold like hotcakes and I recall selling at least 5 or 10 to various customers in Delaware. They are good machines if not abused. A problem I faced with them is that folks kept trying to get PM45 performance out of the PM25 and that's not going to happen. A 250lb machine can-not / will-not cut like an 850lb machine but that did not stop people from trying. As a result of misuse, I ate a lot of warranty work. I also have the 1236 lathe. The 45/9xx series mills along with the 1236 lathe are workhorses. I had several each at one point while doing custom work for the yacht/marina community so they nibbled on equal amounts of stainless steel, carbon steel and aluminum all day long.

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Re: Muriatic Acid: 1. Mill Scale: 0

Postby motox » Sat Oct 14, 2017 7:40 am

most of my stuff is in aluminum and I'm in no rush so light cuts are perfect.
very happy with the machine.
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Re: Muriatic Acid: 1. Mill Scale: 0

Postby cj737 » Sat Oct 14, 2017 8:05 am

RayCJ wrote:As for the acid... Not sure where people got the impression I was attempting to dilute it. Simply not the case. I was using it full strength. FWIW, the stuff available at Lowes (which is what I happen to have) is a 30% solution. As I recall during my college days, only higher mole fraction solutions tend to flash-over.

Ray

I didn’t interpret what you were doing afterwards as “dilution”, only rinsing the surface. But my “misunderstanding” or confusion arose from adding water to acid (by rinsing full strength acid) to flush the table surface. That’s all. And I’m not suggesting that you’re not correct in your use, as I stated, I was “under the impression”. I’m still young enough to learn something everyday (though my grey hair and achy bones belie that statement) :D
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Re: Muriatic Acid: 1. Mill Scale: 0

Postby RayCJ » Sat Oct 14, 2017 10:36 am

cj737 wrote:
RayCJ wrote:As for the acid... Not sure where people got the impression I was attempting to dilute it. Simply not the case. I was using it full strength. FWIW, the stuff available at Lowes (which is what I happen to have) is a 30% solution. As I recall during my college days, only higher mole fraction solutions tend to flash-over.

Ray

I didn’t interpret what you were doing afterwards as “dilution”, only rinsing the surface. But my “misunderstanding” or confusion arose from adding water to acid (by rinsing full strength acid) to flush the table surface. That’s all. And I’m not suggesting that you’re not correct in your use, as I stated, I was “under the impression”. I’m still young enough to learn something everyday (though my grey hair and achy bones belie that statement) :D


It's best to be safe than sorry and procedures discussed on Internet forums should be explicit about safety lest some poor soul get really messed up. FWIW, when I rinsed the top, I had long sleeve shirts and pants and gloves. I was about 7-8 feet away and sprayed gently to keep from getting splashed. Anyhow, 30% concentration acid (70% distilled water) is about as strong as what is commercially available. That can put you in a world of hurt if misused or foolishly mixed with other chemicals.

My main reason for using it non-diluted was because I tried the same procedure with vinegar. After letting it soak for half a day, all it did was make the area smell fresh and clean the way vinegar tends to do. Matter of fact, I might start mopping the shop floors with it. See, you learn something every day!

Anyhow, in hind sight, a weaker solution of muriatic would have worked just fine but maybe taken an hour instead of 15 minutes. Had I gone that route, I certainly would have mixed the acid into an awaiting pail of water.

Be good...


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